From a New York Times obit by Joseph Berger headlined “Andrée Geulen, Savior of Jewish Children in Wartime, Dies at 100”:

Andrée Geulen was a young Belgian teacher at an all-girls boarding school in Brussels in the 1940s when her Jewish students were told that they had to wear uniforms with yellow stars sewn onto them — an antisemitic decree by the occupying Germans to identify and isolate Jews. The students were so humiliated, they clutched notebooks against their chests to hide the stars.

In response, Ms. Geulen, in a show of solidarity, had all the girls in the class — Jews and non-Jews alike — put aprons on over their uniforms.